During recent years, much effort has gone into the development of new products of all types to replace asbestos-containing ones which were widely used for many, many years. In particular, a number of such products have been developed in the field of compressed gasketing material and they employ a variety of fibrous reinforcing materials. The process operations for the manufacture of compressed gasketing materials are such that whatever fibers are used, they must have a substantial degree of resistance to fracture and degradation, as well as the chemical and thermal resistance necessary to perform their sealing function. Among the fibers which have been used with varying degrees of success are ones of carbon, graphite, aramid and glass.
In many applications, some of these new gasketing materials have given sealing results equal to or better than those obtained with the asbestos-containing products of the past. However, as compared to compressed asbestos, a common problem with the new gasketing materials has been a failure to give adequate service life in applications which require the sealing of superheated steam, hot air or other oxidizing fluids. When sealing such fluids, these newer materials show a very substantial weight loss at temperatures typical of such sealing applications and along with this weight loss comes early sealing failure. For processing reasons, it has been necessary in some instances to use particulate filler materials in place of some of the fibrous component and this often brings about greater weight loss at high temperatures as well as generally reduced strength.